1. Field of the Invention
The present invention relates to displays and a method of driving a display, and more particularly to displays having a matrix of electrodes that is scanned line by line to set display data, such as plasma display panels (PDPs), electroluminescence (EL) panels, and liquid-crystal displays (LCDs), and a method of driving such displays.
2. Description of the Related Art
Displays such as PDPs, EL panels, and liquid-crystal displays are getting larger in size and capacity and acquiring full-color display capabilities. As a result, the power consumption of the displays is increasing. It is necessary to minimize the power consumption of the displays.
For example, in a three-electrode surface-discharge alternating-current plasma display panel (3-electrode, surface-discharge AC PDP), a frame is divided into a plurality of sub-frames, in order to display gradations on the PDP. These sub-frames have respective sustain periods whose lengths differ from one another to display gradation levels in combination, and each sub-frame consists of a reset period, an addressing period, and a sustain period. The reset period sets all of the Y-electrodes and applies write pulses to all of the addressing electrodes and X-electrodes. As a result, every cell causes a discharge and neutralizes itself (self-erase discharge).
In the prior art, the Y-electrodes have only been sequentially scanned and this sequence has never been changed. Further, the resolution of displays, i.e., the number of lines on the screen of a display has been increased to increase electrode-to-electrode capacitance.
Power consumption to charge and discharge the electrodes occupies a large part of the power consumption of the PDP. Therefore, the power required to charge and discharge the electrodes must be reduced to minimize the power consumption.
The power required to charge and discharge electrodes is determined by the capacitance, driving voltage, and driving frequency of the electrodes. Among them, only the driving frequency is controllable. A conventional technique drops the driving frequency by masking display data or by reducing the number of sub-frames in each frame. This technique results in reducing the number of gradation levels to be displayed, thereby deteriorating the quality of images to be displayed.
Prior arts and the problems thereof will be explained later with reference to accompanying drawings.
An object of the present invention is to provide a display capable of reducing its current and power consumption without deteriorating the quality of displayed images, and a method of driving such a display.
According to the present invention, there is provided a display having a panel, and first and second electrodes; the first and second electrodes defining a matrix of cells on the panel; the second electrodes, which correspond to lines of the cells, being scanned to select cell lines one by one; the first electrodes being driven to set display data for a selected one of the cell lines, wherein the display comprises a sequence setting unit for setting sequences of scanning the second electrodes; and a sequence selection unit for selecting one of the sequences.
The display may further comprise a difference detection unit for detecting differences between display data set for the cell lines so that one of the sequences that minimizes the differences is selected. The display may further comprise a difference detection unit for detecting differences between display data set for the cell lines; and an upper limit setting unit for setting an upper limit so that one of the sequences that suppresses the differences to below the upper limit is selected. The sequences may be set based on powers of two. The sequence setting unit may divide the second electrodes into blocks and set sequences of scanning the second electrodes block by block; and the sequence selection unit may select one of the sequences in each of the blocks.
The first electrodes may be addressing electrodes, and the second electrodes may be scan electrodes. The display may further comprise an address driver for driving the addressing electrodes; a current/power value detection unit for detecting a current or power value of the address driver; and a sequence changing unit for changing a sequence of scanning the second electrodes to minimize the current or power value.
The display may further comprise a current/power value evaluation unit for evaluating a current or power value of the address driver according to display data set for the cell lines so that one of the sequences that minimizes the current or power value is selected. The display may further comprise a reference value setting unit for setting a reference value so that one of the sequences that suppresses the current or power value to below the reference value is selected.
The display may further comprise a current/power value evaluation unit for evaluating a current or power value of the address driver according to display data set for the cell lines; and a reference value setting unit for setting a reference value so that one of the sequences that suppresses the current or power value to below the reference value is selected. The display may further comprise a current/power value evaluation unit for evaluating a current or power value of the address driver beforehand according to display data set for the cell lines; and a reference value setting unit for setting a reference value so that one of the sequences that suppresses the current or power value to below the reference value is selected. The display may further comprise a display data supplying unit for supplying display data line by line to the first electrodes according to the selected sequence of scanning the second electrodes.
The display may be a plasma display; a frame of display data may be divided into a plurality of sub-frames that are selectively combined to display gradations; and each of the sub-frames may at least include an addressing period and a sustain period. The panel may be a three-electrode surface-discharge alternating-current plasma display panel having third electrodes that run in parallel with the second electrodes and applying an alternating voltage to the second and third electrodes to repeat a sustain discharge.
Further, according to the present invention, there is provided a display having a panel, and first and second electrodes; the first and second electrodes defining a matrix of cells on the panel; the second electrodes, which correspond to lines of the cells, being scanned to select cell lines one by one; the first electrodes being driven to set display data for a selected one of the cell lines, wherein the display comprises a sequence setting unit for optionally setting a sequence of scanning the second electrodes.
The display may further comprise a difference detection unit for detecting differences between display data set for the cell lines so that the second electrodes are scanned in a sequence to minimize the differences. The display may further comprise a difference detection unit for detecting differences between display data set for the cell lines; and an upper limit setting unit for setting an upper limit so that the second electrodes are scanned in a sequence to suppress the differences to below the upper limit. The sequence setting unit may divide the second electrodes into blocks and set a sequence of scanning the second electrodes in each of the blocks.
The first electrodes may be addressing electrodes, and the second electrodes may be scan electrodes. The display may further comprise an address driver for driving the addressing electrodes; a current/power detection unit for detecting a current or power value of the address driver; and a sequence changing unit for changing a sequence of scanning the second electrodes to minimize the current or power value.
The display may further comprise a current/power evaluation unit for evaluating a current or power value of the address driver according to display data set for the cell lines so that the second electrodes are scanned in a sequence to minimize the current or power value. The display may further comprise a reference value setting unit for setting a reference value so that the second electrodes are scanned in a sequence to suppress the current or power value to below the reference value. The display may further comprise a current/power evaluation unit for evaluating a current or power value of the address driver according to display data set for the cell lines; and a reference value setting unit for setting a reference value so that the second electrodes are scanned in a sequence to suppress the current or power value to below the reference value. The display may further comprise a current/power evaluation unit for evaluating a current or power value of the address driver beforehand according to display data set for the cell lines; and a reference value setting unit for setting a reference value so that the second electrodes are scanned in a sequence to suppress the current or power value to below the reference value.
The display may further comprise a display data supplying unit for supplying display data line by line to the first electrodes according to the determined sequence of scanning the second electrodes. The display may be a plasma display; a frame of display data may be divided into a plurality of sub-frames that are selectively combined to display gradations; and each of the sub-frames may at least include an addressing period and a sustain period. The panel may be a three-electrode surface-discharge alternating-current plasma display panel having third electrodes that run in parallel with the second electrodes and applying an alternating voltage to the second and third electrodes to repeat a sustain discharge.
According to the present invention, there is also provided a method of driving a display having a panel, and addressing and scan electrodes, the addressing and scan electrodes defining a matrix of cells on the panel; the scan electrodes, which correspond to lines of the cells, being scanned to select the cell lines one by one; the addressing electrodes being driven to set display data for a selected one of the cell lines, wherein the method comprises the steps of setting sequences of scanning the scan electrodes; detecting a current or power value of an address driver for driving the addressing electrodes; and selecting one of the sequences in accordance with the detected current or power value.
The sequences may be set based on powers of two.
Further, according to the present invention, there is also provided a method of driving a display having a panel, and addressing and scan electrodes, the addressing and scan electrodes defining a matrix of cells on the panel; the scan electrodes, which correspond to lines of the cells, being scanned to select the cell lines one by one; the addressing electrodes being driven to set display data for a selected one of the cell lines, wherein the method comprises the steps of detecting a current or power value of an address driver for driving the addressing electrodes; and optionally setting a sequence of scanning the scan electrodes in accordance with the detected current or power value.
The method may further comprise the steps of dividing the scan electrodes into blocks; and setting a sequence of scanning the scan electrodes in each of the blocks.